How to Fix ValueError: unsupported pickle protocol: 5

Visual Representation of How to Fix ValueError: unsupported pickle protocol: 5

Diagram

ValueError: unsupported pickle protocol:5 error typically occurs when we are trying to load a pickled object using a protocol version not supported by the current Python environment.

To fix the error, upgrade your Python version(such as Python 3.10 or later) that supports pickle protocol 5.

If upgrading is not feasible, and you have control over the pickling process, you can pickle your data using a lower protocol version supported by both the environment where the data is pickled and the environment where it is unpickled.

For example, you could use Protocol 4 (supported in Python 3.4 and later) or an even older protocol if necessary.

Common reasons

Cross-version compatibility

If you are working with a codebase that implicates pickling and unpickling objects across different Python versions, you may encounter the “Unsupported Pickle Protocol: 5″ error when trying to unpickle objects serialized with protocol 5 in an older Python version.

Library compatibility

The main issue is if we update the library or framework to a version that uses the latest pickle protocol while still using an older version of Python. If a compatibility issue occurs, then the chances for this error increase as well.

For example, if data is pickled using Protocol 5 in Python 3.8 or later, and you try to unpickle this data in a Python environment that is version 3.7 or earlier (which does not support Protocol 5), you’ll get an error.

How to fix the error?

The pickle module allows you to specify the protocol version when pickling data, ensuring compatibility across different Python environments. For instance, you can do this:

import pickle

# Specify a protocol version that is compatible with older Python versions
with open('data.pkl', 'wb') as file:
  pickle.dump(your_data, file, protocol=pickle.HIGHEST_PROTOCOL)

However, if an object was pickled using a higher protocol not supported by the Python version you are using, you cannot simply ‘downgrade’ the protocol upon loading. The pickle protocol is determined at the time of pickling, and if a newer protocol is used, an older Python version without support for that protocol will not be able to unpickle the object.

If you encounter a situation where you need to unpickle data in an older Python version, and the data was pickled with a newer protocol, you have a couple of options:

  1. Re-Pickle with a Lower Protocol: The best solution is to re-pickle the object with a lower protocol version in an environment that supports both the original and target protocol versions. You can then transfer this newly pickled object to the environment with the older Python version.
  2. Upgrade the Python Version: Upgrade your Python environment to a version that supports the protocol for pickling the object.

That’s it.

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